Sources and Impurities of Water

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Questions and Answers

Which source of water is considered the purest form but is seldom used in industry?

Sea water

Surface water

Ground water

Rain water (correct)

What type of impurity is caused by metallic substances in water?

Color (correct)

Dissolved gases

Turbidity

Organic matter

Which of the following is NOT a source of water classified in the content?

Rain water

Atmospheric water vapor (correct)

Surface waters

Shallow wells

Which type of dissolved substance in water leads to acid rain formation?

Dissolved gases Signup and view all the answers

From where does ground water typically originate?

Springs and wells Signup and view all the answers

How much percentage of dissolved salts does sea water contain?

3.5% Signup and view all the answers

Which type of impurity refers to extremely fine suspensions like clay and microorganisms?

Turbidity Signup and view all the answers

What is the main reason for sea water's limited use in industrial processes?

Chemical engineering challenges Signup and view all the answers

What is the desirable limit for turbidity in drinking water according to Indian standards?

10 nt units Signup and view all the answers

Which of the following statements about hard water is accurate?

Hard water does not form lather easily due to calcium and magnesium salts. Signup and view all the answers

What is the pH range considered desirable for drinking water according to Indian standards?

6.5 to 8.5 Signup and view all the answers

Which of these is NOT a common cause of hard water?

Sodium chloride Signup and view all the answers

What is one disadvantage of hard water in domestic use?

It reduces fuel efficiency in cooking. Signup and view all the answers

How do soaps react in hard water, according to the content?

Soaps form insoluble precipitates with calcium and magnesium. Signup and view all the answers

What is the acceptable total hardness limit for drinking water in ppm according to IS: 10500?

300 ppm Signup and view all the answers

What effect does hard water have on the textile industry?

It causes wastage of soap during washing. Signup and view all the answers

What is the visual indicator of reaching the end point in the EDTA titration process?

Turning the solution deep blue Signup and view all the answers

What is the initial color of the solution before titration with EDTA?

Wine red Signup and view all the answers

What volume of hard water sample is used in the standardization process?

50 ml Signup and view all the answers

Which of the following volumes represents the EDTA utilized for standardizing the water sample subjected to boiling?

V3 ml Signup and view all the answers

What must be done to the hard water sample before it is measured for EDTA titration?

Boil the water until the volume is reduced Signup and view all the answers

How is the amount of hardness in the sample calculated after titration?

By using the ratio of EDTA volumes based on standardization Signup and view all the answers

What compound's equivalence is represented by the EDTA consumed during the standardization?

Calcium carbonate Signup and view all the answers

What procedure is done after filtering the sample before titration?

Make up the filtrate to 250 ml Signup and view all the answers

What is the main purpose of adding sludge from a previous operation in the tank?

To act as a nucleus for fresh precipitation Signup and view all the answers

How does the continuous cold lime-soda softener ensure the mixing of chemicals and raw water?

By utilizing a paddle stirrer for vigorous stirring Signup and view all the answers

What is a key advantage of the sludge-blanket type softener over the conventional type?

Better removal of silica Signup and view all the answers

In the process of water softening, what happens to the sludge formed during the reaction?

It is allowed to settle and then removed Signup and view all the answers

What does the filtered soft water pass through before it is collected from the top outlet?

A wood-fiber filter Signup and view all the answers

What is the typical retention period required for the conventional cold lime-soda softener?

Four hours Signup and view all the answers

What is the significance of the conical shape of the catalyst or spiractor type cold lime-soda water softener?

It facilitates gravity operation Signup and view all the answers

Which aspect of the sludge-blanket type softener contributes to the waste reduction of lime?

Upward filtration through a sludge blanket Signup and view all the answers

What is the principle behind electrodialysis?

Ions are pulled out by applying direct current through electrodes. Signup and view all the answers

What happens to the salt concentration in the compartments during electrodialysis?

It decreases in one compartment and increases in the other. Signup and view all the answers

Which of the following is NOT an advantage of reverse osmosis?

Removes all dissolved gases. Signup and view all the answers

What type of membrane is traditionally used in reverse osmosis systems?

Cellulose acetate membranes. Signup and view all the answers

What is the role of hydrostatic pressure in reverse osmosis?

It forces solvent from concentrated to dilute side. Signup and view all the answers

What is one major advantage of electrodialysis compared to reverse osmosis?

It has a compact unit design. Signup and view all the answers

What type of water can be treated using both electrodialysis and reverse osmosis?

Brackish water. Signup and view all the answers

How long is the typical life span of the membranes used in reverse osmosis?

About 2 years. Signup and view all the answers

Study Notes

Sources of Water

Chief sources for industrial water supply include rainwater, surface water (rivers, streams, lakes, ponds), groundwater (springs, shallow wells, deep wells), and sea water.
Rainwater is the purest but rarely used in industry.
Surface water can be classified as flowing (rivers, streams) or still (lakes, ponds).
Groundwater is sourced from springs and wells; shallow wells penetrate a single geological layer, while deep wells go through multiple layers.
Sea water presents significant chemical engineering challenges, limiting its use.

Impurities in Water

Water absorbs dissolved gases (oxygen, carbon dioxide) as it precipitates, potentially leading to acid rain.
Soluble crystalloids, such as chlorides and sulfates, are absorbed when water flows over land surfaces.
Seawater contains approximately 3.5% dissolved salts, primarily sodium chloride.
Organic matter in water arises from decomposing plant life and sediment.

Types of Water Impurities

Physical Impurities:
- Color results from metallic substances; turbidity is caused by colloidal and insoluble matter like clay and microorganisms.
WHO and Indian Standards:
- WHO guidelines for drinking water include limits on color, turbidity, pH, and hardness.
- Desirable limits:
  - Color: 5 haze units (up to 50 if toxic).
  - Turbidity: 10 nt units (up to 25 if necessary).
  - pH: 6.5 to 8.5 (also up to 9.2 if necessary).
  - Total hardness: 300 ppm (up to 600 if necessary).

Hardness of Water

Contains dissolved calcium and magnesium salts that cause common boiler issues.
Hard water forms a white scum with soap, while soft water lathers easily.
Primary salts: bicarbonates, sulfates, chlorides of calcium and magnesium.
Hard water disadvantages include:
- Domestic: Difficulty in washing, adverse digestive effects, increased cooking times and fuel usage.
- Industrial: Issues in textile processing due to soap wastage.

Determination of Hardness

Hardness is quantified through titration with EDTA, comparing volumes needed for standard and sample waters.
The method involves boiling samples to convert bicarbonates to carbonates for accurate measurement.

Water Softening Methods

Lime-Soda Process:
- Batch and continuous systems adjust raw water with lime and soda to precipitate hardness-causing minerals.
Zeolite Softening:
- Zeolites exchange sodium ions for hardness ions, effectively softening the water.
Ion Exchange:
- Uses resin beads to replace calcium and magnesium ions with sodium ions, resulting in soft water.

Municipal Water Treatment

Break Point Chlorination:
- A method where chlorine dosage is optimized to ensure pathogen removal while minimizing chemical consumption.

Desalination of Sea Water

Reverse Osmosis:
- Involves applying pressure to force water through a semi-permeable membrane, separating pure water from contaminants.
- Effective in removing ionic, non-ionic, colloidal particles, and high molecular weight organic matter.
Electrodialysis:
- Uses direct current through electrodes and membranes to separate ions from saltwater, creating streams of pure water and concentrated brine.
- Compact and cost-effective method, enhancing efficiency in desalination processes.

Advantages of Water Treatment Methods

Efficient removal of contaminants including colloidal silica and higher molecular weight organic compounds.
Long lifespan of membranes in reverse osmosis, enhancing operational cost-effectiveness.

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Description

Explore the various sources of water used in industry, including rainwater, surface water, groundwater, and seawater. Learn about the different types of water impurities and their impact on water quality. This quiz provides insights into the challenges of using seawater and the factors affecting water purity.